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It's not surprising Butternut (Juglans cinereais) an irritant to some people. It's a very close relative to Black Walnut (Juglans nigra) and English Walnut (Juglans regia). Walnut trees emit a lot of natural herbicides as a way to eliminate competition for nutrients and sunlight where they're growing. The herbicides are probably not all that great for us either.
Rodney

Rodneywt1180b wrote:It's not surprising Butternut (Juglans cinereais) an irritant to some people. It's a very close relative to Black Walnut (Juglans nigra) and English Walnut (Juglans regia). Walnut trees emit a lot of natural herbicides as a way to eliminate competition for nutrients and sunlight where they're growing. The herbicides are probably not all that great for us either.
Rodney

For those that never picked up fresh walnuts, peeled, cracked and ate them the process leaves your hands brown. It takes days for it to wear off. I reckon that the chemicals that cause that wouldn't be very good for you when heated and inhaled.

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any thoughts on Zebra Wood for the bowl? I'm new to pipe making. I've been making knife handles for quite a while and have some in stock that I'd like to use. I heard a guy on You Tube mention that it was pretty toxic but I can't find anything to confirm. I appreciate any feedback.

Aside from toxicity, Zebrawood is really soft and not uniform - akin to pine in my experience. That makes it less than ideal for anything but non-functional adornment.

Frankly, all woods have some various degree of toxicity and carry some amount of resins and stuff, which is why briar is processed the way it is - to remove a lot of those resins. You can easily tell when briar hasn't been processed right. It will smell bad, taste bad, and generally be a disappointment. There are some notable exceptions, like hard maple and fruit woods, and those have been used with some success in the past.

I think Steve hit the nail on the head, and Sas makes a good point about the toxicity of tobacco.
The two environments in which you you must consider toxicity are the workshop and the actual smoking.
There are lots of great stuff that you can use on the shank of a pipe which should not come into proximity of burning tobacco.
For the actual chamber and short piece of shank that is exposed to the heat, it is unwise to use any unproven material or any unknown material. It is easy to obtain briar, morta, olive, some fruit woods and meerschaum, and a bit more difficult to get your hands on Manzanita or mountain laurel (WWII substitutes)- why re invent the wheel or waste your time with unknowns?
As for shank adornments- much wider choice. When you develop difficulty breathing, wheezing, sneezing or a rash- thats your body telling you to stop fiddling with that material.
DocAitch